garmin FR 305 ques - multisport mode

I did.  I am going to see if I can do the same for multisport.

You should have 3 different screens to be able to toggle through regardless of the mode, run/bike/other.  You have 2 General screens and then 1 specific mode screen for either Run/Bike/Other.

I have my Run1 screen setup for 4 displays which includes distance, lap pace, last lap pace, HR

I have my Bike screen setup for 3 displays which includes cadence, speed and HR.

Like a previous post mentioned, setup the autolap for every mile on the run, and I set my bike for every 3 miles.  When in the multisport mode, the bike and run will still use the autolap function. All you need to do is use the right side buttons to scroll between the 3 display screens.  You will always have the 2 General screens.  So when running, scroll to the run screen and you will see what you setup as your Run1 screen.

Pace - Lap   = current laps pace, so if your autolap is setup for 1 mile, it will beep at you and start lap 2 at the end of the first mile.  There is no need to hit the lap button, as you say, it will think the workout is over.

Pace - Last Lap  = last miles pace. 

So theoretically during mile 2, if you have both of those on the display screen, you will see Mile 1's split and your current Mile 2 average.  Once mile 3 starts, you lose the visibility during the race to see mile 1.  So you can only see the current and previous mile.

There is the option to add Pace - Avg, which gives you the average over the whole distance, not quite your mile splits though.